The present invention relates to a device for mechanical connection of a control surface to a fixed structural element of an aircraft.
It relates in particular to articulation and operating means of a control surface on a fixed structural element of a wing element of an aircraft.
In this respect, throughout this description the term “wing element” means any aerodynamic bearing surface of an aircraft, such as a principal wing, or a horizontal or vertical tailplane.
The invention also relates to such a wing element of an aircraft, and an aircraft equipped with same.
A wing element overall has two aerodynamic surfaces which join both at the level of the leading edge and also at the level of the trailing edge of the element.
Such a wing element in general comprises a fixed part attached rigidly to the structure of the fuselage of the aircraft, and a set of mobile elements comprising one or more primary control surfaces and optionally one or more secondary control surfaces.
The fixed part of the wing element is formed from panels forming the aerodynamic surfaces of the element, and an internal structure usually formed by ribs and spars to which the panels are fixed.
Some control surfaces are mounted articulated on the corresponding fixed part of the wing element about an axis of articulation immobile relative to said fixed part. Otherwise expressed, these control surfaces are displaceable according to pure rotation movement relative to the fixed part. These can especially be primary control surfaces such as elevators, rudders, ailerons, or spoiler devices, also called spoilers or airbrakes. These primary control surfaces are connected to the primary flight controls of aircraft and allow the aircraft to maneuver during its different flight phases.
FIG. 1 illustrates highly schematically a rear part of a wing 10 of an aircraft of known type, comprising a fixed part 12 and a primary control surface 14, which is for example an aileron arranged at the trailing edge of the wing 10.
In this example, the control surface 14 comprises two aerodynamic covering walls 16 and 18 joined to each other at the level of the trailing edge 20 of the wing and together forming an acute angle θ so as to prolong respectively the lower wing surface wall 22 and upper wing surface wall 24 of the wing. The control surface 14 also comprises a closing spar 26 arranged near the respective free ends of the two aerodynamic covering walls 16, 18 to which this spar 26 is fixed.
The control surface 14 is mounted articulated on the fixed part 12 by means of hinges (not shown in FIG. 1), which define an axis of articulation 28 of the control surface.
Operating the control surface 14 is ensured by at least one linear jack 30 which can be of pneumatic, hydraulic or electric type. This jack 30 comprises a chassis frame 32 having an end 34 articulated by means of a fork 36 on the rear spar 38 of the wing 10 on which the lower and upper surface walls 22 and 24 of the wing are fixed. The jack 30 also comprises a rod 40 capable of being deployed from the opposite end 42 of the chassis frame 32 and having a free end 43 articulated on a lever 44 connected to the control surface 14. This lever 44 is mounted in rotation about the axis of articulation 28 and with the jack 30 forms a mechanism of crankshaft type for driving the control surface 14 in rotation about the axis of articulation 28 under the effect of displacement in translation of the rod 40 of the jack.
The abovementioned articulations are conventionally of spherical joint type to limit the intensity of parasite moments.
In addition, sealing joints 46 are arranged at the interface between each aerodynamic wall 22, 24 of the fixed part 12 of the wing 10 and the corresponding aerodynamic covering wall 16, 18 of the control surface 14 to limit aerodynamic losses at this level. Each of these joints 46 is fixed to the fixed part 12 so as to be free to slide along the corresponding aerodynamic covering wall 16, 18 of the control surface.
As is shown in FIG. 1, the free end 48, 50 of each aerodynamic covering wall 16, 18 is curved towards the interior of the fixed part 12 of the wing 10 to optimize the regularity of the aerodynamic profile of the wing when the control surface is away from its neutral position, and to facilitate the junction between said aerodynamic covering wall 16, 18 and the corresponding joint 46. The curved part of each wall 16, 18 is formed by a deflector attached to this wall, for example.
But there are disadvantages associated with control surface operating devices of the type comprising a linear jack.
In fact, these mechanisms involve considerable linear operating forces. These forces must be absorbed by the structure of the fixed part of the wing and by the structure of the control surface, which also results in increase in the dimensions and the mass of these structures.
Yet, growing demands for reduction in fuel consumption are compelling aircraft manufacturers to reduce both the weight of future units as well as their drag coefficient, especially by decreasing the thickness of the tailplanes and main wings, to the detriment of the volume available for devices provided for operating the control surfaces.
In addition, increasing operating speeds of the control surfaces made preferable by the development of pilotage laws of aircrafts causes an increase in the required volume of the jacks, which all the more complicates integration of linear jacks within the tailplanes and main wings.
In addition, mechanisms of crankshaft type require articulations, especially comprising spherical joints, for satisfactory operation of this type of mechanism. These articulations contribute to volume, mass and complexity of installation of linear jacks. Similarly, since these articulations are the seat of relative movements during operating of the control surfaces, these articulations are sometimes sources of breakdowns and need regular maintenance to control and re-lubricate them. Requirements for reduction in maintenance costs are encouraging aircraft manufacturers to minimize the number and duration of maintenance tasks. This aim also makes preferable to simplify the operations of assembling and disassembling jacks or actuators dedicated to rotationally driving control surfaces.
In addition, where electrical linear jacks are used, the arrangement of bailers on the aerodynamic surface of the wing element may be required to direct part of the air flowing along the wing element towards the jack so as to limit the risk of overheating of this jack.
These scoops however cause considerable loss of aerodynamic efficacy reflected in overconsumption of fuel.
Patent application FR 2 727 477 A1 proposes a device for operating a control surface comprising a rotary hydraulic actuator and in part rectifies the problems of bulk described hereinabove.
A disadvantage of the solution proposed in this document is that the rotary actuator absorbs the structural forces caused by the aerodynamic load exerted on the control surface. As a consequence this requires an increase in the dimensioning of the actuator and the frequency and extent of maintenance operations needed to verify the status of this actuator.
Also, disassembling of the rotary actuator, especially in light of such maintenance operations, requires prior removal of the control surface supported by the actuator as well as final reassembling of the latter, such that the duration and cost of these maintenance operations are increased.